In recent years, in order to specify a failure portion on a network for a network management, it is often necessary to know a connection relation (a network topology: hereinafter, to be referred to as a topology) between terminals and a switch on the network. A network managing function is typically provided for an IP (Internet Protocol) router used for the Internet in many cases, and is used to determine the topology easily. On the other hand, in LAN (Local Area Network) defined in IEEE802.3 (Ethernet (Registered Trademark)), inexpensive switches are used in many cases. The managing function for specifying the topology is not provided for the switches, and therefore, it is generally difficult to determine the topology. As the conventional techniques for specifying the topology in the LAN, the following methods are known.
As a first conventional technique, a method is typically known of collecting connection data from the switches and determining the topology based on the collected data. The first conventional technique is described in, for example, Japanese Patent Application Publication (JP-A-Heisei, 9-186716), in which each of the switches in the network collects the addresses of the terminals connected to each of interfaces of the switch and the other switches and determines the topology.
As a second conventional technique, a method is known of sequentially inspecting routers/switches on a route between terminals and determining the topology. Conventionally, it is typically known that the topology can be estimated by using a function of sequentially specifying the routers on the route between the terminals, by using Traceroute in an IP level. On the other hand, in the Ethernet (registered trademark), a function of acquiring a response of a frame in the switch has been standardized as IEEE802.1ag, similarly to the Traceroute. Thus, the method similar to the Traceroute can be used to easily estimate the topology.
As a third conventional technique, a method is known in which a packet is transmitted from a certain terminal to a plurality of other terminals, and a correlation between qualities (throughputs, delays, and packet losses) acquired by the packet in the network is inspected to determine the topology in each of the terminals receiving this packet.
However, in the first and second conventional techniques, when a network equipment that does not have a managing function to specify the topology exists in the network, the topology of the portion related to the equipment cannot be specified. In particular, the LAN is typically provided with inexpensive switches with no managing function. The inexpensive switches cannot use the managing function and the IEEE802.1ag in many cases. Thus, it is difficult to specify the topology in the LAN of the typical (inexpensive) configuration.
Also, in the third conventional technique, in order to specify the topology, a topology specifying function is required to be provided for each of the terminals in the network. Thus, the cost increases when the network is configured in which the topology can be specified.